Hydrologic and hydraulic assessment of a proposed multipurpose storage reservoir for flood attenuation and renewable energy storage potential in Ras Al Khaimah, United Arab Emirates

Heavy rains can lead to fast runoff and serious flash flooding in dry and hilly catchments; however, the same region may be suitable for installation of pumped hydro storage (PHS) system. This research explores the feasibility of combining a flood-control reservoir and PHS system within Wadi Al Bih catchment, Ras Al Khaimah, UAE, focusing on flood control and energy storage. A geospatial-hydrologic-hydraulic approach was employed by combining terrain and morphometric analysis using SRTM DEM, HEC-HMS rainfall-runoff model, and HEC-RAS 2D flood modeling. Two scenarios were analyzed: current state of the watershed, and proposed lower reservoir built across Wadi Al Bih and connected to upper PHS reservoir. Proposed flood storage scenario decreased the volume of the simulated floodwater flowing into Ras Al Khaimah city from 28.56 million m3 to 15.25 million m3, that is, a 46.6% decrease, and average flood depth and flood-covered area were decreased by approximately 2.5 m and 25%, respectively. Using the estimated storage volume and a hydraulic head of about 275 m, the potential for energy storage capacity was found to be about 2500 MWh using the given assumptions regarding storage and turbine performance. The findings show that mountainous wadis can offer options for integrating flood detention with renewable energy storage. Nevertheless, the functions of PHS energy storage are theoretical and need to be verified with design calculations, hydrologic data, different storms, and operation optimization.